Motion picture photography and projection is commonly accomplished via a series of still photographs on a strip of sprocketed celluloid film. In the camera, conventions of the motion picture industry call for a standardized frame rate of 24 frames per second, most commonly photographed using a rotating shutter in the camera such that during 360 degrees of shutter rotation, half of the time ( 1/48th of a second) the shutter is open while the film is held fixed in the camera aperture, and the other half of the time the shutter is closed in order for a mechanical movement to transport the film to the next frame, utilizing the perforations on the film to register to either sprockets or claws to move the film as well as hold it in position during each exposure.
For projection, the same frame rate of 24 is used, however the shutter speed is doubled, so that each frame of film is shown twice before proceeding to the next frame. The shutter is often called a “butterfly”, having two openings of 90 degrees each, and two closures of 90 degrees each, thus still rotating at 360 degrees per frame. During one of the shutter closures the film is advanced to the next frame using a mechanical Geneva mechanism, or sometimes a low inertia electric stepper motor. The reason for the double shuttering, which creates a 48 cycle-per-second rate, is to reduce objectionable perceived flicker of the image on the screen, which is limited in brightness to not more than 16 foot lamberts. Projection brighter than 16 foot lamberts reintroduces objectionable perceived flicker.
An objectionable artifact of this double-shuttering of each image frame is a substantial loss of motion continuity due to the fact that the image does not contain new motion position on each flash, resulting in a stroboscopic effect retained in the human retina.
It is common knowledge amongst cinematographers, directors, and editors that frame-to-frame object or image motion must be substantially limited in order to avoid objectionable blurring or strobing. Blurring results from object/image motion that occurs during the shutter opening of 1/48th of a second. Strobing occurs when the image displacement from one frame to the next becomes so great that the eye cannot integrate the sequence of frames into a smooth motion. Screen size is considered a limitation, since frame-to-frame image displacement can become quite objectionable on large screens due to angular displacement of frames on fast action. IMAX is a good example of this phenomenon, and IMAX films routinely slow their camera and object motion in order to avoid objectionable blurring and strobing.
Another shortcoming of the 24 frame standard is that when projecting a 3D movie, which includes two simultaneous projections of left and right eye imagery, if the motion displacement or blur between frames exceeds the displacement between right and left eye convergence angles, the 3D effect is lost and is overcome by blurring and strobing of the image.
An earlier invention and patent for the Showscan system disclosed the photographing and projecting of motion pictures at sixty frames per second. See U.S. Pat. No. 4,477,160, incorporated herein by reference in its entirety. The Showscan system resulted in a solution for the above shortcomings of conventional film, while demonstrably increasing a sense of “liveness” and audience stimulation. Each frame was shown only once, thus not using a double-bladed shutter, and at a shutter opening of 120th of a second, blurring of the recorded image was substantially reduced. At a projection rate of 60 frames per second, there was no apparent flicker at any increased screen brightness, and there was no discontinuity of motion. 3D films photographed and projected in Showscan had no objectionable object/image motion limitations that would adversely affect the 3D illusion.
Nevertheless, worldwide motion picture audiences are accustomed to the 24 frames per second standard, and would find that Showscan is similar to a live broadcast of news or sports, since television is often captured and shown at a rate of 60 interlaced frames. So 24 fps is accepted as a “cinema texture”, while 60 fps would be seen as a “television texture”.
The present invention is intended to take advantage of emerging digital technologies of electronic cinematography and digital projection, which no longer requires adherence to old film-based limitations. In fact, the entire idea of “frames” as individual still photographs projected in rapid succession can now be revised to a new concept of overall fluid image flow. Since the photographed and projected image is, in fact, a matrix of “pixels” at various resolutions, it is now possible to consider a more fluid manner of capturing and projecting imagery on a pixel-by-pixel basis, rather than a frame-by-frame basis. For example, a scene may be digitally photographed without any camera motion whatsoever, thus the overall background would have little or no overall motion. In the foreground, however, a person may be engaged in fighting with another—a common occurrence in movies. Parts of that person, depending upon motion/velocity parameters, may be blurred. A fist, traveling at very high velocity across the screen may be blurred beyond recognition for a number of frames; a face may be blurred beyond recognition as well, as it turns rapidly after the supposed impact (the lack of which has been totally obscured by loss of image clarity). Critical visual information has been lost forever. Sometimes the camera may be moving, as in an exciting car chase sequence, and virtually everything in the frame may be blurred to some degree, often for many frames in a sequence. The result is the visual loss of the very impact that the filmmaker and moviegoer are hoping to experience.
In fact, filmmakers often desire to include in their films as much action as possible in order to instill a sense of participation and excitement in viewers. Yet, a tremendous amount of this action is lost in blur. And in 3D, the image may lose all sense of stereoscopic dimension due to both blur and strobing.
In view of the above, there is a need for an apparatus and method for increasing the clarity and impact of fast action elements of a scene while at the same time preserving the world standard of 24 frame film texture.